Revert "AArch64: Fix emergency spillslot being out of reach for large callframes"

Revert for now as the testcase is hitting a pre-existing verifier error
that manifest as a failure when expensive checks are enabled (or
-verify-machineinstrs) is used.

This reverts commit r322200.

llvm-svn: 322231

1 files changed, 6 insertions, 26 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index ea4bfe7e8d9..d66f7b59a4b 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -142,12 +142,6 @@ static cl::opt<bool> EnableRedZone("aarch64-redzone",
 
 STATISTIC(NumRedZoneFunctions, "Number of functions using red zone");
 
-/// This is the biggest offset to the stack pointer we can encode in aarch64
-/// instructions (without using a separate calculation and a temp register).
-/// Note that the exception here are vector stores/loads which cannot encode any
-/// displacements (see estimateRSStackSizeLimit(), isAArch64FrameOffsetLegal()).
-static const unsigned DefaultSafeSPDisplacement = 255;
-
 /// Look at each instruction that references stack frames and return the stack
 /// size limit beyond which some of these instructions will require a scratch
 /// register during their expansion later.
@@ -173,7 +167,7 @@ static unsigned estimateRSStackSizeLimit(MachineFunction &MF) {
       }
     }
   }
-  return DefaultSafeSPDisplacement;
+  return 255;
 }
 
 bool AArch64FrameLowering::canUseRedZone(const MachineFunction &MF) const {
@@ -197,25 +191,11 @@ bool AArch64FrameLowering::hasFP(const MachineFunction &MF) const {
   const MachineFrameInfo &MFI = MF.getFrameInfo();
   const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
   // Retain behavior of always omitting the FP for leaf functions when possible.
-  if (MFI.hasCalls() && MF.getTarget().Options.DisableFramePointerElim(MF))
-    return true;
-  if (MFI.hasVarSizedObjects() || MFI.isFrameAddressTaken() ||
-      MFI.hasStackMap() || MFI.hasPatchPoint() ||
-      RegInfo->needsStackRealignment(MF))
-    return true;
-  // With large callframes around we may need to use FP to access the scavenging
-  // emergency spillslot.
-  //
-  // Unfortunately some calls to hasFP() like machine verifier ->
-  // getReservedReg() -> hasFP in the middle of global isel are too early
-  // to know the max call frame size. Hopefully conservatively returning "true"
-  // in those cases is fine.
-  // DefaultSafeSPDisplacement is fine as we only emergency spill GP regs.
-  if (!MFI.isMaxCallFrameSizeComputed() ||
-      MFI.getMaxCallFrameSize() > DefaultSafeSPDisplacement)
-    return true;
-
-  return false;
+  return (MFI.hasCalls() &&
+          MF.getTarget().Options.DisableFramePointerElim(MF)) ||
+         MFI.hasVarSizedObjects() || MFI.isFrameAddressTaken() ||
+         MFI.hasStackMap() || MFI.hasPatchPoint() ||
+         RegInfo->needsStackRealignment(MF);
 }
 
 /// hasReservedCallFrame - Under normal circumstances, when a frame pointer is